1. Field of the Invention
The present invention relates to power supply devices and, more particularly, to a battery power supply capable of providing differential DC voltages for computer systems and other electronic devices requiring multiple DC voltages.
2. Description of the Related Art
The need for alternative and backup power sources to regular AC power has increased greatly over the last several years. With the proliferation of computers, such alternative power sources have become especially important. As discussed below, applicant has discovered several deficiencies with existing AC power supplies and the backup power supplies currently available today.
Due to evolving technologies and the abundance of features now available in a single electronic device, newer computers, televisions and other electronic systems often require several different, voltages and currents to operate. For instance, motherboards in todays new generation personal computers require positive and negative 12 volts DC, positive and negative 5 volts DC and positive 3.3 volts DC. Larger computers, typically, require even greater voltages and some require three phase voltages. Additionally, several different currents are required by these motherboards. Such voltages and currents are provided by the computer's power supply, which steps down the Input AC voltage to AC voltages equivalent to those required by the motherboard using transformers, converts the AC voltages to the required positive and negative DC voltages using rectifiers, and then regulates the DC voltages and currents through regulator circuitry.
In many instances, such power supplies are generally useful for their intended purposes. However, almost every computer user, at some time or another, has experienced a loss of data due to power interruptions. Such power interruptions gave rise to the current generation of backup power sources, most commonly known as UPS battery backup systems.
UPS systems consist of batteries and circuitry to convert the batteries' DC output voltage to an AC voltage, which is then supplied to the normal computer power supply to replace the unavailable line AC voltage. However, a large amount of amperage is lost during the DC to AC conversion in the UPS and the subsequent AC to DC conversion in the computer power supply, resulting in a loss of efficiency of approximately fifty percent, as well as unwanted transients. As a result of this loss of efficiency, UPS systems, typically, can only operate for between ten and thirty minutes. Consequently, UPS systems are only intended as a short-term power source to give the user sufficient time to save the applications in use and shut down the computer. Line AC power, when available, is still intended to be the primary power source for the electronic equipment, as well as being necessary to recharge the UPS batteries.
Thus, UPS systems are often useful to provide short term backup power to prevent loss of data. However, in many geographical locations, especially in countries in Central and South America, it is not uncommon to have frequent power outages or even no AC power for most of the day. Such long-term loss of AC power essentially renders UPS systems, as well as the regular internal electronic device power supplies, useless, posing substantial problems for those individuals and entities reliant on computers and other electronic devices.
Various other types of backup power sources have been developed over the years. However, virtually all of these prior art devices operate on the same principle as UPS systems, that is, during the presence of AC line power, the regular electronic device AC to DC power supply provides DC power to the computer, and when AC line voltage is absent or low, AC power is provided to the regular computer AC to DC power supply by backup batteries and DC to AC converters. Thus, these other prior art devices include many of the same limitations and problems discussed with respect to UPS systems and, consequently, are only able to operate for short periods of time.
Portable laptop computer batteries are an example of another common alternative power source. Such portable computers have become a mainstay for businessmen and other professionals and provide computer means during a loss of line AC voltage. However, laptop computer power supplies also have certain inherent limitations which limit the batteries to approximately two hours of continuous operation without recharging and which render them inadequate as an alternative power source for todays newer computers and electronic devices. Specifically, laptop computer batteries fail to directly provide the differential DC voltages required by the newer computers and electronic devices. Laptop batteries, typically, only provide a single output voltage, which is converted or stepped down by regulator circuitry in the motherboard to those voltages required to power the computer components.
If the principals underlying laptop computers and their power systems were utilized with todays newer computers, excessive power would be lost and dissipated as heat, thereby requiring fans to maintain the power supply and surrounding computer components at a safe operating temperature. For example, as stated above, motherboards in todays newer personal computers require positive and negative 12 volts DC, positive and negative 5 volts DC and positive 3.3 volts DC. During normal operation, the positive 5 volt line in these motherboards draw as much as 7 amps (during start-up, as much as 10 amps or more may be drawn). Thus, in converting or stepping down the positive 12 volts to positive 5 volts, 49 watts of power (7 volts.times.7 amps) is wasted and dissipated as heat. Consequently a greater amount of power (49 watts) is wasted in stepping down the positive 5 volts than is actually used by the motherboard on that positive 5 volt line (5 volts.times.7 amps=35 watts). Such a waste of power is not only inefficient, but creates excessive heat and stress on the computer components, thereby shortening their useful life by causing them to operate at a greater temperature than if less heat were being dissipated.
Moreover, laptop computer batteries, like UPS systems, are intended to be only short-term backup power sources, and not replacements for AC power. Normal AC power, when available, is still intended to be the primary power source for laptop computers and is necessary to recharge its batteries.
Another prior art backup device which operates on similar principals to the laptop computer is shown in U.S. Pat. No. 5,578,876, which discloses a computer power system comprising an AC to DC power supply for providing DC power to the computer during the presence of AC line power and a backup power supply for providing DC power from batteries directly to the DC operated components, bypassing the AC to DC power supply, when AC line voltage is absent or low. Although improving over the prior art devices by eliminating the DC to AC conversion circuitry in the backup power supply, this device still does not recognize the loss of power and heat associated with the normal power supply regulator circuitry and, consequently, includes some of the inherent design deficiencies of the prior art power supplies. For instance, in providing DC power from the batteries directly to the DC operated components, regulator circuitry is used to convert or step down the voltage from positive and negative 12 volts to the required positive and negative voltages. As discussed above, if used with todays newer computers, in so doing, 49 watts of power (7 volts.times.7 amps) would be wasted and dissipated as heat when providing positive 5 volts.
Furthermore, this prior art device was designed for use with older computer systems in which the motherboards utilize mechanical switches to power up and power down the computer. On newer computer systems, the motherboard utilizes TTL based logic circuitry to communicate with the power supply to step down on power off and to power on. Because it was designed for motherboards having mechanical switches, this prior art device is incapable of operating with these newer computer motherboards.
Thus, the prior art backup devices teach the use of the regular electronic device AC to DC power supply during the presence of AC line power and single voltage output batteries with regulator circuitry or batteries and circuitry to convert the batteries DC voltages to an AC voltage for use with the regular AC to DC power supply when AC line voltage is absent or low. However, applicant has discovered that a battery DC power supply which provides differential DC voltages directly from the batteries to the electronic equipment and which may serve as a primary power source in place of AC power supplies, as disclosed herein, eliminates or reduces many of the problems inherent in the prior art power supplies.
The prior art, as evidenced by its generally consistent approach in power supply designs, teaches away from such a power supply and fails to recognize these problems. Consequently, there is no suggestion or motivation for one of ordinary skill in the art to modify any of the prior art devices in the manner disclosed by applicant's invention or in any other manner which might address these problems. Such lack of disclosure, suggestion or teaching in the prior art supports the conclusion that part of applicant's invention is the discovery of the problem, that is, the need for a differential voltage battery DC power supply system capable of reducing the inefficiencies, power loss and heat dissipation associated with the prior art power supply devices.
Accordingly, there is a need for a differential voltage battery DC power supply capable of operation during the presence and absence of AC line voltage, which reduces the inefficiencies, power loss and heat dissipation associated with the prior art power supply devices and which provides differential DC voltages directly from the batteries to the electronic device during the presence and absence of AC line voltage, thereby extending the operating time of the backup battery and the useful life of the electronic equipment's components. Any such device should include or should be capable of operation with the logic circuitry necessary to communicate with todays newer motherboards and other control circuits in computers and other advanced technology electronic devices. The present invention is particularly suited to overcome those problems which remain in the art in a manner not previously known.